A gas spring mainly consists of a cylinder tube, a piston in the cylinder tube, a piston rod, a valve rod and so on; gas and oil liquid are stored in the cylinder tube. Since the piston occupies the volume in the cylinder tube, the piston is compressed into the cylinder tube when working, then the piston moves in the axial direction in the cylinder tube to press the oil liquid, then the oil liquid compresses the gas so that the piston reaches the working position; when the external force loaded on the piston rod is removed, the gas recovers and expands, and the expanded gas pushes the oil liquid to reset the piston and move out the piston rod, so that the gas spring realizes a compression motion and a restoration damping motion.
The utility model with application number of CN202402546U discloses a lifting gas spring of a rigid locking seat, as shown in FIG. 2, including a cylinder tube 5, a piston rod 1, a valve body 10 and a valve core 11; a guide sleeve 2 and a guide sealing ring 3 are sleeved on the piston rod 1 and are installed in the cylinder tube 5, one end of the piston rod 1 penetrates out the cylinder tube 5 and the other end has a piston 8, an inner annular tube 6 is fixed in the cylinder tube 5 through a front support 4 having damping air holes 4-1 at two ends and a valve body 10 having a damping oil hole 10-1, the piston 8 is arranged in the inner annular tube 6 in sealing mode and divides the inner annular tube 6 into a front inner gas cavity 18 and a rear inner oil cavity 16, the valve body 10 is connected with the cylinder tube 5 and the inner annular tube 6 in sealing mode, the valve core 11 is installed on the valve body 10 through an abrasion resistant sleeve 15, an oil hole 15-1 is arranged on the abrasion resistant sleeve 15, a valve cover at the front end of the valve core 11 corresponds to a valve seat 9 on the valve body 10, the rear end of the valve core 11 penetrates out the valve body 10 to correspond to a starting rod 13, the starting rod 13 is installed on the rear portion of the cylinder tube 5 through a rear support 12, a floating separator piston 7 is installed between the cylinder tube 5 and the inner annular tube 6 in sealing mode and divides the cavity between the cylinder tube 5 and the inner annular tube 6 into a front outer gas cavity 19 and a rear outer oil cavity 17, the front inner gas cavity 18 is communicated with the front outer gas cavity 19 through the damping air hole 4-1 arranged on the front support 4, and the rear outer oil cavity 17 is communicated with the rear inner oil cavity 16 through the damping oil hole 10-1 on the valve body 10 and the oil hole 15-1 on the abrasion resistant sleeve 15.
As for the above gas spring, the maximum extension length of the piston rod 1 is less than the length of the piston rod 1; in some situations that need bigger extension length, if the above gas spring is to meet corresponding requirements, the sizes of the inner cylinder tube, the outer cylinder tube and the piston rod must be increased, so as to increase the extension length of the piston rod; however, this method makes the gas spring difficult to apply to many occasions, for example, the gas spring with long size cannot apply to occasions that need short travel, while the gas spring with short size cannot apply to occasions that need long travel, consequently each occasion needs a gas spring of one size.